Extremely high RPM startups

[NightRider97]

Hey guys.
I have an issue with my 97 GST. When I start the car after its had time to completely cool down the engine will immediately run up to 2000-2500rpm. It's been doing this to a certain extent for a while now, but its just getting flat out rediculous now. It started out at like a high idle of 1000rpm, but 2500 I know there's something wrong there.
Just so you know, I just replaced the Idle speed controller at the beginning of last year and the car probably has less than 5k on it since then. And no its not some cheap parts house controller, its the genuine deal Mitsu part. So I doubt its that. Is there another electronic piece of crap that controls the idle speed?

After the car is completely warm it runs normal.

 

[mindset]

Replace your Coolant Temp Sensor

 

[kottyking]

How about the BISS screw? There is an o ring type seal that gets ruined over time that can leak air and cause wierd ide.

 

[->PrOjEcTGS<-]

Yep... try correctly setting your BISS so that it brings the idle down to 750rpm when the engine is fully warm.

2G BISS Adjustment

It could also be a vacuum leak. Vac leaks will cause a high idle.

 

[NightRider97]

Thanks for the replies guys!
WOW, I guess I'll be taking the thing to a shop. Man I hate other people touching my car, but I don't have the real scan tool, all I have is a pocketlogger. I need to have a couple other things done that I can't do as well, so oh well I guess. I can handle literally anything on older carb'd engines and even most older diesel engines. Heck I even stripped this engine down and rebuilt the entire valve train and timing components when I had a head gasket blow, but there's some computer stuff with this car I just can't tackle. Thanks for the quick replies though.

 

[rbwtrans]

Search "FIAV valve"

 

[mindset]

If you're extremely bored. Here's my dilemma. ALOT of good information.
http://www.dsmtuners.com/forums/newbie-forum/327709-biss-grounding.html

 

[rbwtrans]

Check out the link in post #22 of minset's link "BISS grounding" This explains a lot about the FIAV and how it works. I just solved a high idle problem on my 91 gs with this info.

 

[greentsiawd13]

simple things first check the tension on the throttle cable first b4 you spend any more $ i had the same problem and i changed alot of parts b4 adjusting the throttle cable runs great ever since wish i wouldnt have spent $ on dumb parts for a shot in the dark let us know what it is
good luck

 

[95'RS-T]

i agree with projectGS double check your vac lines